Persistence of intracellular and extracellular changes after incompletely suppressing expression of the R789C (p.R989C) and R992C (p.R1192C) collagen II mutants.

Mutations in COL2A1 produce a spectrum of disorders whose hallmark feature is alterations in skeletal development. Attempts to counteract the effects of collagen mutations at the molecular level have been relatively ineffective due to the inability to selectively suppress a mutant allele, and failure to deliver a sufficient number of cells expressing wild-type collagen. Moreover, these approaches are hampered because the minimal therapeutic conditions that would allow extracellular matrix remodeling and recovery of cells from stress are not known. Here, we employed a tetracycline-inducible system for expressing the R789C or R992C collagen II mutants, allowing us to decrease the production of mutant proteins by 25, 50, 75, or 100% with respect to their initial production. Through analysis of intracellular and extracellular parameters we have shown that affected cell/matrix systems are able to recover from mutation-induced aberrations only when 100% expression of mutant collagens is shut off, but not if the expression of small amounts of mutant molecules persists in the system. Our data suggest that efficient remodeling of tissues affected by the presence of thermolabile collagen mutants may depend on their complete elimination rather than on partial reduction.

Delivery Outcomes of Pregnant Patients With Inflammatory Bowel Diseases Compared With the General Population and With Women With Other Autoimmune Diseases at a Tertiary Care Center.

BACKGROUND: Variable data have suggested that pregnant women with inflammatory bowel diseases (IBD) are more likely to have cesarean deliveries and adverse pregnancy outcomes than the general population. The aim of this study was to describe the rates of cesarean delivery and adverse pregnancy outcomes among patients with IBD as compared with patients with other autoimmune diseases and with the general population. METHODS: Pregnant patients with IBD, those with non-IBD autoimmune diseases, and control patients were identified. Baseline demographics, disease characteristics, medication use, and delivery outcomes were recorded in a retrospective manner. The primary outcome was overall rate of cesarean delivery; secondary outcomes included rates of planned and unplanned cesarean delivery, delivery complications, preterm delivery, and fetal complications. RESULTS: Ninety-three women with IBD were age-matched to 376 control patients; 38 women with other autoimmune diseases were also identified. Women with IBD had higher rates of cesarean delivery (47%) when compared with control patients (31%; P < 0.0001) but not when compared with women with other autoimmune diseases. There were high rates of planned cesarean deliveries for IBD-related factors in the IBD cohort. Women with IBD did not have increased rates of adverse delivery or fetal outcomes. CONCLUSIONS: Women with IBD have higher rates of cesarean delivery than the general population and rates similar to those of women with other autoimmune diseases. Planned cesarean delivery plays an important role in maintaining continuity and sphincter control in select situations, but a diagnosis of IBD does not mandate cesarean delivery.

Retinoic acid receptors are required for skeletal growth, matrix homeostasis and growth plate function in postnatal mouse.

The retinoic acid receptors alpha, beta and gamma (RARalpha, RARbeta and RARgamma) are nuclear hormone receptors that regulate fundamental processes during embryogenesis, but their roles in skeletal development and growth remain unclear. To study skeletal-specific RAR function, we created conditional mouse mutants deficient in RAR expression in cartilage. We find that mice deficient in RARalpha and RARgamma (or RARbeta and RARgamma) exhibit severe growth retardation obvious by about 3 weeks postnatally. Their growth plates are defective and, importantly, display a major drop in aggrecan expression and content. Mice deficient in RARalpha and RARbeta, however, are virtually normal, suggesting that RARgamma is essential. In good correlation, we find that RARgamma is the most strongly expressed RAR in mouse growth plate and its expression characterizes the proliferative and pre-hypertrophic zones where aggrecan is strongly expressed also. By being avascular, those zones lack endogenous retinoids as indicated by previous RARE reporter mice and our direct biochemical measurements and thus, RARgamma is likely to exert ligand-less repressor function. Indeed, our data indicate that: aggrecan production is enhanced by RARgamma over-expression in chondrocytes under retinoid-free culture conditions; production is further boosted by co-repressor Zac1 or pharmacologic agents that enhance RAR repressor function; and RAR/Zac1 function on aggrecan expression may involve Sox proteins. In sum, our data reveal that RARs, and RARgamma in particular, exert previously unappreciated roles in growth plate function and skeletal growth and regulate aggrecan expression and content. Since aggrecan is critical for growth plate function, its deficiency in RAR-mutant mice is likely to have contributed directly to their growth retardation.

Reducing the effects of intracellular accumulation of thermolabile collagen II mutants by increasing their thermostability in cell culture conditions.

Mutations in collagen II are associated with spondyloepiphyseal dysplasia, a group of heritable diseases whose common features include aberrations of skeletal growth. The mechanisms through which mutations in collagen II affect the cartilaginous tissues are complex and include both intracellular and extracellular processes. One of those mechanisms involves cellular stress caused by excessive accumulation of misfolded collagen II mutants. We investigated whether stabilizing the structure of thermolabile R789C and R992C collagen II mutants would improve their secretion from cells, thereby reducing cellular stress and apoptosis. Employing glycerol and trimethylamine N-oxide (TMAO), chemicals that increase the thermostability of collagen triple helices, we demonstrated that those compounds function as chaperones and stabilize the R789C and R992C mutants, accelerate their secretion, and improve cell survival. Our study provides a scientific basis for considering misfolded triple helices of collagen mutants a target for reducing the deleterious effects caused by their excessive intracellular accumulation.

Cells expressing partially unfolded R789C/p.R989C type II procollagen mutant associated with spondyloepiphyseal dysplasia undergo apoptosis.

We investigated the effects of the presence of R75C (p.R275C), R519C (p.719C), R789C (p.R989C), and G853E (p.G1053E) type II collagen (COL2A1) mutants, associated with distinct forms of spondyloepiphyseal dysplasia (SED), on the biological processes occurring in chondrocytic cells harboring those mutants. Mutant-specific biological responses of cells were initiated by activating tetracycline (Tet)-dependent expression of type II collagen mutants. Employing microscopic and biochemical assays, we determined that cells expressing the thermolabile R789C (p.R989C) type II collagen mutant undergo apoptosis. In contrast, in cells expressing the thermostable R75C (p.R275C), R519C (p.719C), and G853E (p.G1053E) mutants, apoptotic markers were not apparent. We also demonstrated that the R789C (p.R989C) mutant formed atypical complexes with endoplasmic reticulum (ER)-resident chaperones, thereby indicating an "unfolded protein response" (UPR) of cells harboring this specific mutant. Apoptotic changes were also demonstrated by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) and cleaved caspase 3 assays in the growth plates of mice harboring the R992C (p.R1147C) substitution in type II collagen. Based on these results, we propose that the intracellular presence of structurally altered type II collagen mutants could activate an apoptotic response, thereby limiting cell survival. By analyzing the response of cells to the altered structure of collagen mutants, our study contributes to better understanding the molecular basis of the pathological changes seen in vivo at the tissue level.

R992C (p.R1192C) Substitution in collagen II alters the structure of mutant molecules and induces the unfolded protein response.

We investigated the molecular bases of spondyloepiphyseal dysplasia (SED) associated with the R992C (p.R1192C) substitution in collagen II. At the protein level, we analyzed the structure and integrity of mutant molecules, and at the cellular level, we specifically studied the effects of the presence of the R992C collagen II on the biological processes taking place in host cells. Our studies demonstrated that mutant collagen II molecules were characterized by altered electrophoretic mobility, relatively low thermostability, the presence of atypical disulfide bonds, and slow rates of secretion into the extracellular space. Analyses of cellular responses to the presence of the mutant molecules showed that excessive accumulation of thermolabile collagen II was associated with the activation of an "unfolded protein response" and an increase in apoptosis of host cells. Collectively, these data suggest that molecular mechanisms of SED may be driven not only by structural changes in the architecture of extracellular collagenous matrices, but also by intracellular processes activated by the presence of mutant collagen II molecules.

The Modifier of hemostasis (Mh) locus on chromosome 4 controls in vivo hemostasis of Gp6-/- mice.

Platelet glycoprotein VI (GPVI) is a key receptor for collagens that mediates the propagation of platelet attachment and activation. Targeted disruption of the murine gene Gp6 on a mixed 129 x 1/SvJ x C57BL/6J background causes the expected defects in collagen-dependent platelet responses in vitro. The extent of this dysfunction in all Gp6(-/-) mice is uniform and is not affected by genetic background. However, the same Gp6(-/-) mice exhibit 2 diametrically opposed phenotypes in vivo. In some mice, tail bleeding times are extremely prolonged, and thrombus formation in an in vivo carotid artery ferric chloride-injury model is significantly impaired. In other littermates, tail bleeding times are within the range of wild-type mice, and in vivo thrombus formation is indistinguishable from that of control mice. Directed intercrosses revealed that these phenotypes are heritable, and a genome-wide single-nucleotide polymorphism scan revealed the most significant linkage to a single locus (8 megabases) on chromosome 4 (logarithm of the odds [LOD] score = 6.9, P < .0001) that we designate Modifier of hemostasis (Mh). Our results indicate that one or more modifier genes in Mh control the extent to which in vivo platelet thrombus formation is disrupted by the absence of platelet GPVI.

End-of-life care: a special calling for case managers.

A peaceful, pain-free death with final days spent on one's own terms is a wonderful and measurable outcome of individual case management. Advocacy in life and especially in death should be at the very heart of case management.